The invention relates generally to power units and more specifically to an arrangement in a power unit for a grid pulsed O-type microwave tube.
In high-power radar transmitters, high-voltage power units are used to power grid-pulsed, O-type microwave tubes, e.g., travelling-wave tubes. Such tubes have a cathode and at least one collector, and a power unit for such tubes comprises a cathode power unit and a collector power unit for each collector.
The cathode power unit has two output terminals. One of the output terminals is to be connected to the cathode of the microwave tube, while the other output terminal is connected to a ground terminal. Between the output terminals of the cathode power unit, a capacitor is connected.
The collector power unit also has two output terminals. One of these output terminals is to be connected to the collector of the microwave tube, while the other output terminal is interconnected with that one of the output terminals of the cathode power unit that is to be connected to the cathode of the microwave tube. Between the output terminals of the collector power unit, a capacitor is also connected.
Both the cathode power unit and the collector power unit normally comprise converters, high-voltage transformers, rectifiers and filters.
For good performance of the microwave tube, a high quality cathode voltage is required.
However, in such power units, there are problems with crosstalk from the collector power unit to the cathode voltage. When the capacitor connected between the output terminals of the collector power unit is recharged by the collector power unit, an undesired current appears through the capacitor connected between the output terminal of the cathode power unit due to undesired stray capacitances between the collector power unit and ground, mainly between the high-voltage transformer in the collector power unit and ground.
This undesired current results in undesired cathode voltage variations.
An object of the invention is to eliminate crosstalk from the collector power unit to the cathode voltage. This is attained in accordance with the invention by connecting the output terminals of the collector power unit to the associated capacitor via non-capacitive impedances as well as to the ground terminal via decoupling capacitors. As a result, crosstalk caused by the collector power unit across the output terminals of the cathode power unit is eliminated.
This is attained in accordance with the invention by connecting the output terminals of the collector power unit to the associated capacitor via non-capacitive impedances as well as to said ground terminal via decoupling capacitors.
Hereby, crosstalk caused by the collector power unit across the output terminals of the cathode power unit will be eliminated.